It is believed that in ascending mountains difficult breathing is
sooner felt upon snow than upon rock; and M. Boussingault, in his
account of the ascent of Chimborazo, attributes this to the sensible
deficiency of oxygen contained in the pores of the snow, which is
exhaled when it melts. The fact that the air absorbed by snow is
impure, was ascertained by De Saussure, and has been confirmed by
Boussingault’s experiments.--_Quarterly Review_, No. 202.